EFFECTS OF MORBID CELL-GROWTHS. 491 dinated to that of the system at large; and the presence of insubordinate cells implies disease. Thus, small-pox arises from the intrusion of a species of cell, foreign to that community of cells of which the body consists, and which, absorbing nourishment from the blood, rapidly multiplies by spontaneous division, until its progeny have diffused themselves throughout the tissues; and if the excreting energies of the constitution fail to get rid of these aliens, death ensues. In certain states of body, indigenous cells will take on new forms of life, and by continuing to reproduce their like, give origin to parasitic growths, such as cancer. Under the microscope, cancer can be identified by a specific element, known as the cancer-cell. Besides those modifications of cell-vitality, which constitute malignant diseases, there occasionally happens another in which cells, without any change in their essential nature, rebel against the general governing force of the system; and, instead of ceasing to grow, whilst yet invisible to the naked eye, expand to a considerable size, sometimes even reaching several inches in diameter. These are called Hydatids or Acephalocysts,* and have, until lately, * * "The primitive forms of all tissues are free cells, which grow by imbibition, and which develop their like from their nucleus of hyaline. All the animal tissues result from transformations of these cells. It is to such cells that the acephalocyst bears the closest analogies in physical, chemical, and vital properties. We may, with some truth, say that the human body is primarily composed or built up of acephalocysts; microscopical, indeed, and which, under natural and healthy conditions, are metamorphosed into cartilage, bone, nerve, muscular fibre, &c. When, instead of such change, the organic cells grow to dimensions which make them recognizable to the naked eye, such development of acephalocysts, as they are then called, is commonly connected in the human subject with an enfecblement of the controlling plastic force, which, at some of the weaker points of the frame, seems unable to direct the metamorphosis of the primitive cells along the right road to the tissues they were destined to form, but permits them to retain, as it were, their embryo condition, and to grow by the imbibition of the surrounding fluid, and thus become the means of in been taken for internal parasites or entozoa. Still closer appears the relationship between tissue-cells and the lowest independent organisms, on finding that there exists a creature called the Gregarina, very similar in structure to the Hydatid, but which is admitted to be an entozoon. Consisting as it does of a cell-membrane, inclosing fluid and a solid nucleus, and multiplying as it does by the spontaneous fission of this nucleus and subsequent division of the cell-walls, the Gregarina differs from a tissue-cell merely in size, and in not forming part of the organ containing it.* Thus there may coexist in the same organism cells of which that organism is constituted, juriously affecting or destroying the tissues which they should have supported and repaired. I regard the different Acephalocysts, therefore, as merely so many forms or species of morbid or dropsical cells."-Profeesor Owen's Hunterian Lectures. * "Schleiden has viewed these Gregarinæ as essentially single organic cells, and would refer them to the lowest group of plants. And here, indeed, we have a good instance of the essential unity of the organic division of matter. It is only the power of self-contraction of tissue, and its solubility in acetic acid, which turn the scale in favour of the animality of the Gregarine; they have no mouth and no stomach, which have commonly been deemed the most constant organic characteristics of an animal." "1846, Henle and others have questioned the title of the Gregarina to be regarded as an organic species or individual at all, or as any thing more than a monstrous cell: thus applying to it my idea, propounded in 1843, of the true nature of the acephalocyst." "1848, Kollicker has recently published an elaborate memoir on the genus, in which good and sufficient grounds are given for concluding that the Gregarina not merely resembles, but actually is an animated cell; it stands on the lowest step of the animal series, parallel with that of the single-celled species of the vegetable kingdom. The Gregarina con. sists, as Schleiden and others have well shown, of a cell-membrane, of the fluid and granular contents of the cell, and of the nucleus with (ccasional) nucleoli. The nucleus is the hardest part, resisting pressure longest, like that of the Polygastrian. It divides, and its division is followed by spontaneous fission."-Professor Owen's Hunterian Lectures. ANALOGIES OF THE LIVING AND SOCIAL ORGANISM. 493 others which should have helped to build it up, but which are insubordinate or partially separate, and others which are naturally separate, and simply reside in its cavities. Hence we are warranted in considering the body as a commonwealth of monads, each of which has independent powers of life, growth, and reproduction; each of which unites with a number of others to perform some function needful for supporting itself and all the rest; and each of which absorbs its share of nutriment from the blood. And when thus regarded, the analogy between an individual being and a human society, in which each man, whilst helping to subserve some public want, absorbs a portion of the circulating stock of commodities brought to his door, is palpable enough. A still more remarkable fulfilment of this analogy is to be found in the fact, that the different kinds of organization which society takes on, in progressing from its lowest to its highest phase of development, are essentially similar to the different kinds of animal organization. Creatures of inferior type are little more than aggregations of numerous like parts-are moulded on what Professor Owen terms the principle of vegetative repetition; and in tracing the forms assumed by successive grades above these, we find a gradual diminution in the number of like parts, and a multiplication of unlike ones. In the one extreme there are but few functions, and many similar agents to each function: in the other, there are many functions, and few similar agents to each function. Thus the visual apparatus in a fly consists of two groups of fixed lenses, numbering in some species 20,000. Every one of these lenses produces an image; but as its field of view is extremely narrow, and as there exists no power of adaptation to different distances, the vision obtained is probably very imperfect. Whilst the mammal, on the other hand, possesses but two eyes; each of these includes numerous appendages. It is compounded of several lenses, having different forms and duties. These lenses are capable of various focal adjustments. There are muscles for directing them to the right and to the left, to the ground and to the sky. There is a curtain (the iris) to regulate the quantity of light admitted. There is a gland to secrete, a tube to pour out, and a drain to carry off the lubricating fluid. There is a lid to wipe the surface, and there are lashes to give warning on the approach of foreign bodies. Now the contrast between these two kinds of visual organ is the contrast between all lower and higher types of structure. If we examine the framework employed to support the tissues, we find it consisting in the Annelida (the common worm, for instance) of an extended series of rings. In the Myriapoda, which stand next above the Annelida, these rings are less numerous and more dense. In the higher Myriapoda they are united into a comparatively few large and strong segments, whilst in the Insecta this condensation is carried still further. Speaking of analogous changes in the crustaceans, the lowest of which is constructed much as the centipede, and the highest of which (the crab) has nearly all its segments united, Professor Jones says-"And even the steps whereby we pass from the Annelidan to the Myriapod, and from thence to the Insect, the Scorpion, and the Spider, seem to be repeated as we thus review the progressive development of the class before us." Mark again, that these modifications of the exo-skeleton are completely paralled by those of the endo-skeleton. The vertebra are numerous in fish and in the ophidian reptiles. They are less numerous in the higher reptiles; less numerous still in the quadrupeds; fewest of all in man: and whilst their number is diminished, their forms and the functions of their appendages are varied, instead of being, as in the eel, nearly all alike. Thus, also, as it with locomotive organs. The spines of the echinus SUBDIVISION OF SOCIAL FUNCTIONS. 495 and the suckers of the star-fish are multitudinous. So likewise are the legs of the centipede. In the crustaceans we come down to fourteen, twelve, and ten; in the arachnidans and insects to eight and six; in the lower mammalia to four; and in man to two. The successive modifications of the digestive cavity are of analogous nature. Its lowest form is that of a sack with but one opening. Next it is a tube with two openings, having different offices. And in higher creatures, this tube, instead of being made up of absorbents from end to end-that is, instead of being an aggregation of like parts-is modified into many unlike ones, having different structures adapted to the different stages into which the assimilative function is now divided. Even the classification under which man, as forming the genus Bimana, is distinguished from the most nearly related genus Quadrumana, is based on a diminution in the number of organs that have similar forms and duties. Now just this same coalescence of like parts, and separation of unlike ones-just this same increasing subdivision of functions-takes place in the development society. The earliest social organisms consist almost wholly of repetitions of one element. Every man is a warrior, hunter, fisherman, builder, agriculturist, toolmaker. Each portion of the community performs the same duties with every other portion; much as each portion of the polyp's body is alike stomach, skin, and lungs. Even the chiefs, in whom a tendency toward separateness of function first appears, still retain their similarity to the rest in economic respects. The next stage is distinguished by a segregation of these social units into a few distinct classes -soldiers, priests, and labourers. A further advance is seen in the sundering of these labourers into different castes, having special occupations, as amongst the Hindoos. And, without further illustration, the reader will at once perceive, that from these inferior types of society up to |